27: The Main Protaganist

The first two notes (Db-D) that the solo horn plays are a semitone apart; when heard with the basses (Bb) they outline a minor third to a major third. This semitone cell journeys through Lightfall in many guises.

(Gustave Dore)

It would be tedious in the extreme to list every occurrence of the semitone cell so here are just a few pointers:

Part One
The minor/major third can be observed:
- as Db-D-Db in the horn against the pedal Bb throughout the opening of Part One (b4-19)
- Also as Bb-B against G (b38-51)
- The horn against the trombones at b62-64 and at b102-104

The semitone cell gets an extended workout from the horn from b116 until it is the only interval from the third beat of b137-140

There are also crucial moments where the two semitone notes are played against each other such as when the first violins introduce a B over the sustained Bb in the other strings at b21-25; the Bb against B in b30-31 (both G major and G minor), which is again heard at the end of the movement, unresolved (b160-161).

The octatonic scale, that is stepped through by the cycling instruments, has a semitone as every second note.

Part Two
Once again the first two notes played by the horn are a semitone apart. The horn melody compresses itself during three phrases until it is a semitone at letter B, then opens out again. Obviously as this theme occurs through the course of the movement the semitone travels with it.

Six of the cycle of seven chords contains a semitone dissonance, I, II, III and IV as the major seventh against the root, VI and VII as the major ninth against the minor third. So the semitone is woven into the fabric of Part Two with only chord V giving slight relief from the rich harmonic colour of major sevenths and ninths.

Because most of Part Two does not modulate we become trained to feel that only the eight notes used are “right”. This heightens our sensitivity to the insistent intrusion of the C natural. Three of the cycle chords, as well as the A major substitute chord, contain C#; three of the chords contain neither C nor C#, thus supporting whichever of the two notes has last been heard; only one of the chords contains a C natural. This means that only two chords (I and II) support a tonality with C natural, while five chords (III-VII) support a tonality with C#. We have a semitone conflict.

From b293 the horn begins to respond to this conflict, being thrown from one to the other by the prevailing orchestra’s harmony until (b320 to the end) the semitone is all that’s left. In the last two bars the semitone is once again operating as the minor/major third of the harmony.

The Trill (not to be confused with this or this)
I have already pointed out that both parts begin with the semitone in the horn, Part One in low register, stepping upwards, Part Two in high register stepping down. There is also another semitone connection between the two movements: the low upward trill Db-D at the end of the main section of Part One (b140), is echoed by the high downward trill C#-C at the very end of Part Two.